生长抑素受体亚型在人内分泌肿瘤上的效应器偶联

Effector coupling of somatostatin receptor subtypes on human endocrine tumors.

作者信息

Kubota A, Yamada Y, Kagimoto S, Seino S, Seino Y

机构信息

Department of Metabolism and Clinical Nutrition, Kyoto University, Japan.

出版信息

Metabolism. 1996 Aug;45(8 Suppl 1):42-5. doi: 10.1016/s0026-0495(96)90078-5.

DOI:10.1016/s0026-0495(96)90078-5

PMID:8769378

Abstract

Effector coupling of somatostatin receptor subtypes sst1 and sst2 was examined in a reconstituted system. Forskolin-stimulated cyclic adenosine monophosphate (cAMP) formation was inhibited 66% by somatostatin (SRIF-14) in CHO cells expressing somatostatin receptor 1(sst1) (CHO-SR1), but not sst2, in a dose-dependent manner with an ED50 of 1 x 10(-9) mol/L SRIF-14. The inhibition was blocked by pertussis toxin (PTX), indicating that sst1 is coupled to adenylyl cyclase via PTX-sensitive Gi protein. In CHO cells, Gi alpha 2 and Gi alpha 3 mRNAs were detected. In adenylyl cyclase assays, 1 mumol/L SRIF-14 caused a 16% inhibition of forskolin-stimulated adenyly cyclase activity. Preincubation with Gi alpha 3, but not Gi alpha 1/Gi alpha 2, antiserum blocked this inhibition. By contrast, sst2 is coupled to adenylyl cyclase via Gi alpha 1. In cells expressing sst2 with Gi alpha 1(CHO-SR2G1), SRIF-14 significantly inhibited forskolin-stimulated cAMP formation by 53% and with an ED50 at 4 x 10(-9)mmol/L SRIF-14, which was completely blocked by PTX; ED50 values for sst1 and sst2 agree with the IC50 values in binding assays. In CHO-SR1, the rank of potency of agonists affecting adenyl cyclase was SRIF-14 = SRIF-28 > RC 160 > SMS 201-995. In CHO-SR2G1, the rank was RC-160 > SRIF-14 = SRIF-28 > SMS 201-995.

摘要

在一个重组系统中研究了生长抑素受体亚型sst1和sst2的效应器偶联。在表达生长抑素受体1（sst1）的CHO细胞（CHO-SR1）中，生长抑素（SRIF-14）以剂量依赖方式抑制佛司可林刺激的环磷酸腺苷（cAMP）生成，ED50为1×10⁻⁹ mol/L SRIF-14，抑制率达66%，而在表达sst2的细胞中则无此现象。百日咳毒素（PTX）可阻断该抑制作用，表明sst1通过对PTX敏感的Gi蛋白与腺苷酸环化酶偶联。在CHO细胞中检测到了Giα2和Giα3 mRNA。在腺苷酸环化酶分析中，1 μmol/L SRIF-14使佛司可林刺激的腺苷酸环化酶活性受到16%的抑制。与Giα1/Giα2抗血清预孵育不能阻断该抑制作用，而与Giα3抗血清预孵育可阻断。相比之下，sst2通过Giα1与腺苷酸环化酶偶联。在表达sst2和Giα1的细胞（CHO-SR2G1）中，SRIF-14使佛司可林刺激的cAMP生成显著抑制53%，ED50为4×10⁻⁹ mmol/L SRIF-14，且完全被PTX阻断；sst1和sst2的ED50值与结合分析中的IC50值一致。在CHO-SR1中，影响腺苷酸环化酶的激动剂效力排序为SRIF-14 = SRIF-28 > RC 160 > SMS 201-995。在CHO-SR2G1中，排序为RC-160 > SRIF-14 = SRIF-28 > SMS 201-995。